1. Field of the Invention
This invention relates to an apparatus designed to assist a person with focal limb weakness, in particular those having a foot-drop type of disability with weakness or paralysis of dorsiflexion and eversion of the foot and extension of the toes. In particular the present foot drop aid is quickly and easily attached on the foot or shoe and onto the leg of the patient employing reliable, long use coil springs for the motive force.
Persons who have sustained a stroke, peripheral nerve injury, or suffer from diseases such as multiple sclerosis, et al., generally incur certain neuromuscular pathological conditions because of damage to the nerves which innervate the muscles involved. This damage occurs centrally in the brain and/or spinal cord, or locally to peripheral nerves, such as those found in the leg, resulting in paralysis or partial paralysis in varying degrees of severity to different parts of the body. Generally, the distal joints are proportionately weaker than the more proximal joints (proximal meaning close to the midpoint of the body). Foot-drop is characterized in that a person, who otherwise has sufficient muscular control to move his foot relative to his ankle in plantar flexion (a downward push off motion), lacks sufficient muscular control to subsequently effect a dorsiflexion motion to raise the foot back up for the next step. Also usually evidenced in persons having foot-drop is the diminished capacity to move the foot in what is termed eversion, or rotating the outer part of the foot in an upward manner.
Paralysis, in any degree, of the ankle and the mid-tarsal joint (just distal to the ankle), and the resultant foot-drop, present greater problems because of the independent movement required of them in walking. Ankle motions are dorsi-flexion (up) and plantar flexion (down), and mid-tarsal joint motions are inversion (inward turning) and eversion (outside edge of the foot turned up). Paralysis or partial paralysis for any of the reasons described herein usually impair the ankle and mid-tarsal joint such that dorsi-flexion and eversion are weaker than plantar flexion and inversion. Where a foot-drop problem is present, walking without the assistance of a brace or support will result in the front (toe) portion of the foot dragging along the ground after the leg and foot have completed the plantar flexion portion of the gait. Therefore, a need exists for a foot-assist mechanism which selectively provides dorsiflexion support for the foot by compensating for the weakened muscles while allowing the functioning flexor muscles or portions thereof to continue to contract to their fullest extent.
2. Related Art
A number of devices have been provided to date to alleviate foot-drop which includes short-leg braces having metal uprights, metal stirrups, molded calf cups, etc. Rigid devices such as U.S. Pat. No. 3,986,501 to Schad are static in nature in that they maintain the foot in a relatively fixed position in relation to the leg (which is never greater than 90 degree.) at all times so that the entire lower leg from calf to toes moves en masse as a rigid structure being propelled and supported by the person's knee, hip and spine, thereby producing an awkward gait and immobilize working muscles to a degree, contributing to disuse atrophy or earlier degeneration.
More recently several devices which will aid the functioning of those muscles directly effected by a disabling condition, such as those described hereinbefore, but which allows full range of motion of the foot and usage of those muscles either not effected or only partially effected, such as described in U.S. Pat. Nos. 4,817,589; 5,257,959; 6,602,217 and 7,354,413 have employed elastomeric components for foot lift. The '959, '217 and '413 devices required attachment directly on the foot while the '217 device requires special attachment means on a shoe.
It is an advantage of the present invention as it relates to a foot lit apparatus that in addition to allowing full range of motion of the foot and usage of those muscles either not effected or only partially effected, that it provides a more reliable and longer use foot lift component. It is a further advantage of the present foot lift device that is easily attached by the patient directly to the foot for use with a shoe or directly onto any shoe worn by the patient.
Finally, it is intended to provide a foot-drop assist device which is lightweight, relatively inconspicuous, easy to use, and very inexpensive to make and maintain.
A person having a foot-drop type disability wearing the present foot lift apparatus can use relatively unaffected muscles without hindrance or discomfort to their fullest extent, e.g., by extending the foot (plantar flexion), while at the same time enjoying the benefits of a convenient selectively-active assist mechanism which will help them to walk normally. The present foot lift device is particularly useful to stroke victims since the muscles used to raise the foot (dorsi-flexion) and turn it outward (eversion), both of which are required in walking, are nearly always affected by those persons suffering residual paralysis as a result of a stroke.